A growing awareness of the earth began in the 1960s. The connection between astronomy/cosmology and environmentalism is a very clear one. When NASA’s Apollo astronauts took photos of the earth from space for the first time (including the iconic “Earthrise”, an image taken by Apollo 8 astronauts during the first human space flight to orbit the moon in 1968), a never before experienced sense of awe was felt by humans who could truly see the sheer beauty of their home for the first time. The environmental movement was born out of a convergence of factors, including mounting fears over nuclear weapons. The photos the astronauts took transcended borders, and impacted people in a way political arguments never could. It began in the United States, but in the decades since its inception has become a global phenomenon, celebrated in at least 144 countries worldwide. Many of these countries recognize the accompanying Earth Week, the week leading up to April 22.

“Earthise”, 1968

In honor of Earth Day, I’d like to draw attention to the importance of preservation by highlighting one of the most visceral and affecting descriptions of Earth I’ve seen. This description comes from the introduction to Carl Sagan’s 1994 book A Pale Blue Dot: A Vision of the Human Future in Space.

Credit: NASA / JPL

“Pale Blue Dot”, 1991

According to the Planetary Society, of which Carl Sagan was a co-founder:

“This excerpt from A Pale Blue Dot was inspired by an image taken, at Sagan’s suggestion, by Voyager 1 on February 14, 1990. As the spacecraft left our planetary neighborhood for the fringes of the solar system, engineers turned it around for one last look at its home planet. Voyager 1 was about 6.4 billion kilometers (4 billion miles) away, and approximately 32 degrees above the ecliptic plane, when it captured this portrait of our world. Caught in the center of scattered light rays (a result of taking the picture so close to the Sun), Earth appears as a tiny point of light, a crescent only 0.12 pixel in size.”

“We succeeded in taking that picture [from deep space], and, if you look at it, you see a dot. That’s here. That’s home. That’s us. On it, everyone you ever heard of, every human being who ever lived, lived out their lives. The aggregate of all our joys and sufferings, thousands of confident religions, ideologies and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilizations, every king and peasant, every young couple in love, every hopeful child, every mother and father, every inventor and explorer, every teacher of morals, every corrupt politician, every superstar, every supreme leader, every saint and sinner in the history of our species, lived there on a mote of dust, suspended in a sunbeam.

The earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that in glory and in triumph they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of the dot on scarcely distinguishable inhabitants of some other corner of the dot. How frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Our posturings, our imagined self-importance, the delusion that we have some privileged position in the universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity – in all this vastness – there is no hint that help will come from elsewhere to save us from ourselves. It is up to us. It’s been said that astronomy is a humbling, and I might add, a character-building experience. To my mind, there is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly and compassionately with one another and to preserve and cherish that pale blue dot, the only home we’ve ever known.”

-Carl Sagan

Earth, for all of its resilience, is a fragile ecosystem. Science is miraculous, and life on earth is the most improbable of possibilities. While the search for astrobiology continues in earnest–efforts not least of which have been made by Carl Sagan’s Search for Extraterrestrial Intelligence, or SETI—so far, our one planet is all we have and the only place in the universe that we know with certainty contains life. As Sagan said, the responsibility of stewardship of our home is “up to us” because “there is no hint that help will come from elsewhere to save us from ourselves”. Not only should we direct our efforts at treating out fellow human beings with “kindness” and “compassion”, but we should “preserve” and “cherish” Earth. This is the message of Earth Day, a message we celebrate every April, but one we should carry with us every day.